The source of released MIF is unknown, however, since MIF is constitutively expressed in the basal and intermediate layers of the urothelium[10], and MIF mRNA is upregulated in the urothelium during inflammation[11], it is likely that the urothelium is either responsible for MIF release during cystitis or contributes a significant portion of the MIF released. This evidence concerns the gene MIF and chronic cystitis.